Demons Play In the Night
by Prime627
Summary: Optimus' brother lives in his head, and Nemesis isn't happy about that. He wants to feel what Optimus feels. He's tired of being in a fish bowl, so when he finds out how to get out without his brother's interference, he decides to warm the berth with the femme Optimus has been drooling over for years in secret. What are brothers for?
1. Chapter 1

Nemesis moved around inside Optimus' processor. He had been in there ever since they were born, always there and always watching and listening. He wanted to experience what his brother felt, but all he could do was observe.

That was, until he took control, but he wasn't good at keeping control. Optimus would always tuck him back inside his processor and pat his figurative helm like the _good little parasitic brother_ he was.

But things were going to change.

Optimus was sleeping, his processor blank, peppered with a few dreams. This was the perfect time to take over. He pushed his limbs into Optimus' and he flicked his brother's optics open.

He was in control now. He laid Optimus in the back of his helm and he covered him in darkness. Then he got up and walked out into the hall.

Because Nemesis took over, the blue and red armor paint on Optimus turned purple and black, and Optimus' blue optics darkened to red.

He walked into the main room and stopped when he saw Arcee working late. He racked his brother's memories, searching for information on the little femme staying awake late. Optimus had nothing to share on that matter, so he smirked and flashed crooked, sharp denta.

"Hello, child."

Arcee's helm snapped up and she blinked at Nemesis. There was no reason to be surprised. Optimus fought Nemesis every day, and everyone got to see his mishap of a brother.

"Hello, Nemesis. What may I do for you?"

He pressed her back into a wall, pinching her little winglets. "I'm out for the night, and I wondered if you would show me a good time."

She pushed at his chest softly, but her optics were cloudy with delight. Her body heated up easily, and it showed Nemesis that she was eager for a berthmate, someone to frag her nightly.

And Nemesis had all night long to abuse her little valve.

He was rubbing at her panel, and he licked his servo clean of her lubricants. "Go to your quarters and lay down, child..."

She hurried off to her berth and she waited patiently, trembling in delight.

Nemesis pulled his panel back and looked down at his spike. His brother thought it was a weapon, so he didn't lay down with a femme or a mech. He used to plead with his spike whenever it hardened, and he begged it to _play nice_. But now, Nemesis was ready to use this spike.

"Alright, spike," Nemesis purred as he wrapped his servo around its thick length. His thumb rubbed along the tip, catching the pearls of purple fluid and he flicked them off his digits, smirking softly as he walked to stand in Arcee's doorway.

She was laying on her back, a servo bent over her chest so that the digits brushed between her breastplates. She was breathing heavy, her optics dim as she stared at Nemesis.

His optics dropped between her legs to the dripping valve. He smirked and crawled onto her berth. Her legs spread and wrapped around his hips, guiding him closer.

They were silent, staring at each other. Nemesis couldn't believe she had seduced this little femme, and Arcee couldn't believe she was being seduced, but she ground her hips gently on his, his spike prodding her entrance.

Nemesis pushed her hips down. No way was he about to let this night slip away.

He lowered his mouth to her neck, kissing and licking her cords. His digits ran down her body, over her belly, and down her to valve where he pinched and pulled her exterior sensor there, just above her opening. She whined and gripped his back, tugging and clawing.

He pulled up and kissed between her breastplates, licking up to her lips where he kissed her gently and tested her valve.

He grunted. Way too tight there. He couldn't ease into her, couldn't make her arch up the way he wanted. He wanted her to burn and shiver, but if he penetrated now, she would wail and squirm.

So Nemesis lowered his helm and kissed her valve gently. She whined and spread her legs wide, her optics wide and she sat up to watch him, touching his helm as he licked and lapped at her dripping petals.

He kissed, licked, sucked, and fingered her valve as he purred. She overloaded quickly, and he flicked her lubricant off his face with his digits, chuckling gently as he kissed her hard.

His spike prodded her valve again, and this time, her valve stretched around it.

He thrusted into her, pinning her servos above her helm while he forced his brother's body and hers to overload at the same time.

They did, and Arcee went limp beneath him while he panted and laid a servo on her belly. He kissed her gently as he pulled out and he laid down beside her.

"Mm," he sighed. "When I wake, I will not be Nemesis. I will be Optimus, and he will be...embarrassed."

Arcee clung to him, pressing her face into his chest. "Will you come as often as possible?"

"I'll try," he said softly and he kissed her.

For years, he had craved physical attention, and now he had it, but only for a little while tonight, and if everything worked out, he would have it each and every night after this.

But during the day, he had to give up the body to his brother.

 **ooo**

Optimus woke up and sighed gently. Then he sat up in horror. Where was he? He had gone to sleep in his quarters, but where was he now? Not in his quarters, that's for sure!

Arcee was nestled against him, and his optics widened at that realization. No, he pleaded as he lifted the blanket.

There was his spike, limp and pressed against his thigh. He touched it, and looked at his digits. Covered in purple fluid and lavendar lubricant. He shuddered and looked at Arcee.

Her lubricant was spattered all over her valve, hips, and thighs. A closer examination revealed oral lubricant and he cried out.

Nemesis was laughing at him.

 **The demons play in the night, brother...oh, and congratulations. You're not a virgin, and she's not dead.**

His fear of losing control while he fragged a femme, and in the end killing her, overwhelmed him until he heard Arcee purr and twitch. She was...pleasureably exhausted.

Optimus stared at her for a long time before he got up and snuck out of the room, shaking. What had his brother done?

 **You can thank me now, brother...**

He locked himself into his quarters. "What have you made me do?"

 **You got fragged. Now let me relax. I need to prep myself for tonight.**

Before Optimus could ask what that meant, Nemesis was gone and he sat there, stunned. _He had fragged Arcee? With my body?_

 **ooo**

Nemesis walked to Arcee, smirking down at her.

"You've come back."

"Optimus fell asleep."

Arcee smiled up at him gently. "He left rather quick..."

Nemesis smirked from audio to audio and he laid down with her, determined to make her cry out louder than the last time he laid with her.


	2. Chapter 2

**There are two versions of Nemesis that I write about. Either he's his own bot, or he's stuck in Optimus' head. If you ask me, I like when the brothers fight over one body, one identity. Optimus gets most of the control, but Nemesis wants to fight for it, and he tries to take it over every chance he gets.**

Optimus was determined not to wake up in Arcee's quarters again. So he busied himself with work, and forced his optics to stay wide open. But, Nemesis coaxed him to fall asleep.

He walked into his mate's quarters and he stopped at her fearful optics.

"I'm carrying," she mumbled. Tears were forming in her optics. "I thought I couldn't carry...I told Cliffjumper I couldn't...but I could...I can..." She was holding the blankets over herself, so Nemesis couldn't see if she was serious or not.

And then the blankets twitched, and he walked closer after shutting the door. He pulled the blankets back and smiled at her belly.

It was rounded perfectly. She must have gotten carrying when he first fragged her, which was wonderful. That meant his brother's body wasn't sterile after all, and he could stop teasing him.

He sat beside her. "That's wonderful...I mean, sad that you didn't frag with Cliffjumper when you had the chance, but you're carrying now, I mean..." He pulled her to her pedes. "Wonderful..."

He stroked her belly, expecting to just feel one, but instead he felt two pairs of pedes and four servos pressing against his own. He looked at her with wide optics.

"What's wrong?" She clutched her belly.

"Well..." He stood slowly. "Either our child is horribly, horribly defected, or we have twins."

"Split-sparks?"

"Arcee, don't be silly." He smiled and he kissed her. "No, not split-sparks. Just twins. Regular, ordinary twins."

She purred gently and pushed back at his chest. "Not ordinary."

Nemesis smiled, and then his optics shorted out as Optimus took over. He had woken up, and was secretly worming back into his body. The last step was to force his brother back, and once that was complete, he got his body back.

He saw Arcee's belly and he wailed, backing up. "Look what I have done to you..."

Arcee scoffed. "You didn't. Nemesis did."

He whimpered gently and he touched her belly, feeling the twins. Optimus felt like getting sick, but he held his Energon in his tank and he fell to his knees. "Forgive me. I should have had Ratchet zap him out or something...look at you, Arcee!"

"I'm carrying. It's not like it's a curse."

"You are carrying _my_ sparklings!"

" _You_ aren't." Arcee grabbed his face. "Nemesis sired them, and Nemesis and I can take care of them. You just have to let him out during the night."

Optimus gaped at her. "It is not like I can _let him out_. He takes control. Have you ever been in a fishbowl? It is like you are there, mostly. You can hear and see, but you cannot feel. Nemesis feels like he is in a fishbowl in the morning, and I feel like I am sleeping in a fishbowl at night. It is not a pleasant feeling."

Arcee opened her mouth to apologize, but then Nemesis took control.

"Sorry about that," he said as he locked his brother away. "He can be a strutless baby sometimes."

Arcee nodded and she laid down in her berth, coaxing him to lay down beside her.

They laid like for as long as possible, and then Optimus bolted, but it was later than the last time.

Nemesis was getting better at keeping his brother under control, and it scared Optimus.

Would there be a day when Optimus barely saw light?


End file.
